a real Acid of Colalt. 103 



Now, as the result of these expcriincnts is, that cobalt 

 tannot be converted into acid by the most powerful and 

 most active means emoloved for changmg mto acidri those 

 metals susceptible of acidification, and as it is not impro- 

 bable that nature may produce some circumstances tavour- 

 able to the formation of cobaltic acid, though there is not 

 the least reason to suspect that this can be tlie case m the 

 preparation of the crav oxide of cobalt, nothing remains 

 but to admit that the 'cobaltic acid ot Brugnatclh was an 

 union of arsenical acid with other substances; and this 

 conjecture is the less hazarded, as it is well known that a 

 oxide of cobalt contains more or less arsenic, and in aU 

 probability in the state of acid. It now remams to show, 

 if possible, that this union of arsenical acid is capable ot 

 producins the phenomena which Brugnatelh observed m 

 re<rard to his supposed acid of cobalt. This, m my opi- 

 nion, will be best accomplished by the phajuomena whicb 

 occurred in the following experiuRnts. 

 Experiment IX. 

 Four hundred parts of pure liquid ammonia \%cre poured 

 over fifty grains of arseuiate of cobalt obtained by precipila- 

 tion ancrdi"-c^^ted two hours, during which the mixture 

 sometimes was made to boil. Alter the liquor, \\hich wai 

 of a red colour inclinintj to blue, was separata.1 by filtration, 

 the same quantity of ptue liquid ammonia was poured oyer 

 the undissolved residuum, and the process repeated. 1 he 

 colour of the liquor thus obtained was not so bltie. fh*; 

 residuum had lost about two-thirds m weight, and had be- 

 come blueish red ; whereas the arscniatc ot cobalt has a 

 pale rose colour. The two fluids obtained were evaporated 

 ioadram, durinir which operation the greater part ot the 

 dissolved oxide of cobalt was separated ot a grayish blue 

 colour. The filtered liquor wa* of a cochincai red, and ex- 

 hibited the following pluenomeiia : 



1st, A little of it being evaporated to dryness in a porce- 

 lain dish, suffered ammonia to escape, and also deposited a 

 little o-ravish green oxide of cobalt. Tlie residuum, diluted 

 vMth distilled water and filtered, had scarcely a reddish co- 

 lour as Iku'rmttelli observed in a specimen ot his cobaltic 

 acid, and luuj a sharp acid taste, a property which he ascribes 

 in general to his cobaltic axid- It still eoutained a little 

 ammonia, and some traces of cobalt. 



'id, It gave a perceptible red colour to litmus paper, but 

 no acid taste was perceived in It. 111 



3d. It precipitated lime water, without being redisbolved, 



